Silicone release agents are well known in the art. Numerous silicones are commercially available, as are liners coated with a layer of silicone. However, these silicones have various drawbacks including controlling the amount of release desirable. Frequently, silicones provides what is known in the art as "premium release", meaning that they exhibit extremely low release values, i.e., 4-60 g/inch of width. These low values are not always desirable, especially for release coatings to be used on the back surfaces of adhesive tapes. This type of back surface coating is known as "low adhesion backsize" or LAB. A controlled release having a value of from 60 to about 2000 g/inch of width to the adhesive is often desired, so that the tape will not prematurely unwind. Silicones are available in both solvent curable, and uv-curable systems. Many nonsilicone polymers such as urethanes are used as LABs because of their higher release force than the silicones. Various modifications of silicones have been attempted for use in adhesive tapes, such as binding them with polymers having higher releases, as in U.S. Pat. Nos. 3,3288,482, 3,527,659 and the like.
Pattern release coatings have been of interest for many years for the goal of controlling release in silicones. In DE-PS 8 55 746, the idea of making a release coating which formed a pattern was disclosed. However, no method for accomplishing the pattern coating was disclosed, nor exemplified. Likewise, UK Patent Application GB 2,209,148 A, published May 4, 1989, discloses a two-layer self-adhesive label having a self-adhesive base which provides a non-adherent area. The nonadherent area is described as printed with a pattern UV cured release panel. However, no method for making such a pattern is disclosed or claimed.
In U.S. Pat. No. 3,503,782, a differential release paper is made by applying a full coating of a first release agent, and a second partial coating of a differing release agent. It is stated that the second coating may be provided in the form of a pattern. In this manner, the surface is provided with a variable release force. However, this requires the complete coating of the surface with one release agent, typically requiring several processing steps and waste of a certain amount of silicone release agent which is under area covered by the second agent.
In DE 3727 078 A1, Beiersdorf, published Feb. 23, 1989, it is disclosed that the problems of making and using this type of coating have never been resolved. It is disclosed in this publication that two layer screen-printed silicone release coatings may be made on a substrate by priming the substrate with a commercial primer, known to have a low release value. Primers disclosed include isocyanate crosslinked polyvinyl acetate, and solutions of chromium stearate complexes mixed with polyvinyl alcohol. The silicone may then be overcoated onto the primer. The silicone is coated using a screen with a sieve size of 10-450 mesh, and typically covers 20-80% of the surface of the primer.
Thus, all of the patterned release liners for which methods of manufacture are disclosed above, have required the use of a primer, or second fully coated layer of release agent.
Processes are also known for pattern printing of other compounds onto substrates, i.e., adhesives. In U.S. Pat. No. 3,741,786, pressure-sensitive adhesive transfer tapes are disclosed having a plurality of substantially non-contiguous raised pressure-sensitive adhesive segments. This construction is disclosed to allow the pressure-sensitive segments to be transferred.
An objective of the present invention is to provide a release article having a patterned coating for use with adhesive tapes and other applications which does not require the use of a primer with the silicone release agent.
Another objective of the present invention is to provide a plurality of articles having smooth controlled release varying from about 20 g/inch to well over 500 g/inch.